Historical Data Strategy

As of 2026-05-29

Decide history disposition by access tier (hot 2-3y full granularity · warm 3-7y aggregated · cold statutory-only archived) before cutover — not by migrating everything at full granularity. Four options: full migrate (hot only), aggregate-and-migrate (warm 80/20), archive to NLS/object store (cold), read-only legacy sunset with a hard date. Retention is a legal input (DE tax 10y §147 AO; GDPR forbids over-retention) — get the matrix signed by legal first. "Do we need 12 years of daily granularity?" is the money question; aggregating to monthly cuts warm storage ~10×. Saving the client money is the durable rate justification.